The perpetration of fraudulent emergency service calls has risen to such significant levels that law enforcement and emergency responses are been dangerously hampered. Accordingly, the detection and reduction of fraudulent emergency service calls is of ever increasing importance. Detection and reduction of fraudulent emergency service calls begins with identifying the source of the fraudulent call. Historically this identification has been based on the unique calling party number (CgPN) assigned to the subscriber initiating the call. The CgPN may be the same as the call back number delivered to the Public Service Answering Point (PSAP) in association with the emergency service call. While this process proves workable for most land line devices, identifying the source of a fraudulent wireless call is much more difficult.
The CgPN for a mobile station (e.g., mobile phone) that originates any call is usually the mobile directory number (MDN), which is dialable, of the mobile station. For instance, the MDN is dialed by a caller and used to route a call through the network to the wireless subscriber's home system. At the subscriber's home system, the home location register (HLR) contains the mobile subscriber identifier (MSID) associated with the subscriber's MDN. The MSID, not the MDN, is then used to route the call through the network to the serving wireless system and page the subscriber. The subscriber's MDN is provided by the home system to the serving system in a separate data file called the subscriber profile. Typically, the MSID is either a 10-digit mobile identification number (MIN) or a 15-digit International Mobile Subscriber Identifier (IMSI) programmed into a mobile station by the service provider with whom the mobile station user has entered into a service agreement. Accordingly, an alternative way to identify the source of a wireless emergency service call is the MSID assigned to the mobile station by the service provider. However, the MSID is not necessarily a dialable number.
Unfortunately, either or both of the MDN and the MSID of a mobile station originating a wireless service call might be unknown—a so-called non-coded mobile station. The MDN or MSID could be unknown for many reasons, including (a) the mobile station was never intended to be registered (there are such phones to use for emergency calls only), (b) the phone is new and has not yet been registered with a service provider or (c) the subscription has expired and the mobile station is no longer registered with a service provider. Some mobile phones also support a removable User Identity Module (R-UIM) or Subscriber Identity Module (SIM) that may contain the MSID and the MDN. If the R-UIM or SIM are not in the mobile station, then the mobile station can still be used to place an emergency call. However, there is no MDN or MSID known to the mobile station or the serving system to provide the PSAP as a call back number.
Current standards permit a mobile station without a permanent MSID or without a MDN known to the serving system to originate an emergency service call. Accordingly, those who wish to perpetrate emergency service call fraud have turned to using cell phones and other forms of mobile stations. With current fraud prevention techniques, such a perpetrator; particularly those using non-coded mobile stations, are extremely difficult to recognize.